During Linux operation and maintenance, sometimes it is necessary to transfer local files to other servers, or obtain files from other servers to the local server. The scp command can realize the mutual transfer of files between the local server and the remote server.
In order to improve the security of data when copying across machines, scp uses ssh connection and encryption. If ssh password-free login is configured between machines, there is no need to enter a password when using scp.
scp is the abbreviation of secure copy, which is a secure remote file copy command based on ssh login under Linux system, which can copy files or directories between Linux servers. Commands similar to it have cp, but cp is only copied locally, not across servers, and scp transmission is encrypted, which may slightly affect the speed. When the server hard disk becomes read-only read only system, you can use scp to move the file out. In addition, scp does not take up resources very much and does not increase the system load much. At this point, rsync is far behind it. Although rsync is a bit faster than scp, when there are many small files, rsync will cause very high hard disk I/O, and scp basically does not affect the normal use of the system.
1. Command format
Enter scp help to view the command format.
$ scp help
usage: scp [-12346BCpqrv] [-c cipher] [-F ssh_config] [-i identity_file]
[-l limit] [-o ssh_option] [-P port] [-S program]
[[user@]host1:]file1 ... [[user@]host2:]file2
2. Option meaning
Enter man scp to view the meaning of specific options.
$ man scp
SCP(1) BSD General Commands Manual SCP(1)
NAME
scp — secure copy (remote file copy program)
SYNOPSIS
scp [-12346BCpqrv] [-c cipher] [-F ssh_config] [-i identity_file] [-l limit] [-o ssh_option] [-P port] [-S program] [[user@]host1:]file1 ...
[[user@]host2:]file2
DESCRIPTION
scp copies files between hosts on a network. It uses ssh(1) for data transfer, and uses the same authentication and provides the same security as ssh(1).
scp will ask for passwords or passphrases if they are needed for authentication.
File names may contain a user and host specification to indicate that the file is to be copied to/from that host. Local file names can be made explicit
using absolute or relative pathnames to avoid scp treating file names containing ‘:’ as host specifiers. Copies between two remote hosts are also permitted.
The options are as follows:
-1 Forces scp to use protocol 1.
-2 Forces scp to use protocol 2.
-3 Copies between two remote hosts are transferred through the local host. Without this option the data is copied directly between the two remote
hosts. Note that this option disables the progress meter.
-4 Forces scp to use IPv4 addresses only.
-6 Forces scp to use IPv6 addresses only.
-B Selects batch mode (prevents asking for passwords or passphrases).
-C Compression enable. Passes the -C flag to ssh(1) to enable compression.
-c cipher
Selects the cipher to use for encrypting the data transfer. This option is directly passed to ssh(1).
-F ssh_config
Specifies an alternative per-user configuration file for ssh. This option is directly passed to ssh(1).
-i identity_file
Selects the file from which the identity (private key) for public key authentication is read. This option is directly passed to ssh(1).
-l limit
Limits the used bandwidth, specified in Kbit/s.
-o ssh_option
Can be used to pass options to ssh in the format used in ssh_config(5). This is useful for specifying options for which there is no separate scp
command-line flag. For full details of the options listed below, and their possible values, see ssh_config(5).
AddressFamily
BatchMode
BindAddress
CanonicalDomains
CanonicalizeFallbackLocal
CanonicalizeHostname
CanonicalizeMaxDots
CanonicalizePermittedCNAMEs
CertificateFile
ChallengeResponseAuthentication
CheckHostIP
Cipher
Ciphers
Compression
CompressionLevel
ConnectionAttempts
ConnectTimeout
ControlMaster
ControlPath
ControlPersist
GlobalKnownHostsFile
GSSAPIAuthentication
GSSAPIDelegateCredentials
HashKnownHosts
Host
HostbasedAuthentication
HostbasedKeyTypes
HostKeyAlgorithms
HostKeyAlias
HostName
IdentitiesOnly
IdentityAgent
IdentityFile
IPQoS
KbdInteractiveAuthentication
KbdInteractiveDevices
KexAlgorithms
LogLevel
MACs
NoHostAuthenticationForLocalhost
NumberOfPasswordPrompts
PasswordAuthentication
PKCS11Provider
Port
PreferredAuthentications
Protocol
ProxyCommand
ProxyJump
PubkeyAcceptedKeyTypes
PubkeyAuthentication
RekeyLimit
RhostsRSAAuthentication
RSAAuthentication
SendEnv
ServerAliveInterval
ServerAliveCountMax
StrictHostKeyChecking
TCPKeepAlive
UpdateHostKeys
UsePrivilegedPort
User
UserKnownHostsFile
VerifyHostKeyDNS
-P port
Specifies the port to connect to on the remote host. Note that this option is written with a capital ‘P’, because -p is already reserved for pre‐
serving the times and modes of the file.
-p Preserves modification times, access times, and modes from the original file.
-q Quiet mode: disables the progress meter as well as warning and diagnostic messages from ssh(1).
-r Recursively copy entire directories. Note that scp follows symbolic links encountered in the tree traversal.
-S program
Name of program to use for the encrypted connection. The program must understand ssh(1) options.
-v Verbose mode. Causes scp and ssh(1) to print debugging messages about their progress. This is helpful in debugging connection, authentication, and
configuration problems.
EXIT STATUS
The scp utility exits 0 on success, and >0 if an error occurs.
SEE ALSO
sftp(1), ssh(1), ssh-add(1), ssh-agent(1), ssh-keygen(1), ssh_config(5), sshd(8)
HISTORY
scp is based on the rcp program in BSD source code from the Regents of the University of California.
AUTHORS
Timo Rinne <tri@iki.fi>
Tatu Ylonen <ylo@cs.hut.fi>
BSD November 6, 2020 BSD
Three, the Chinese interpretation of command parameters
- -1 Force scp command to use protocol ssh1.
- -2 Force scp command to use protocol ssh2.
- -3 Transfer data between two remote hosts through the local host. Without this option, the data will be copied directly between the remote hosts. Note: This option does not support progress bar display.
- -4 Force the scp command to use only IPv4 addressing.
- -6 Force the scp command to only use IPv6 addressing.
- -B Use batch mode (don’t ask for the transmission password or phrase during transmission).
- -C allows compression. (Pass the -C flag to ssh to turn on compression).
- -p Keep the modification time, access time and access permissions of the original file.
- -q Does not display the transfer progress bar.
- -r Copy the entire directory recursively.
- -v Display output in verbose mode. scp and ssh(1) will display the debugging information of the whole process. This information is used to debug connection, verification and configuration issues.
- -c cipher Use cipher to encrypt data transmission. This option will be passed to ssh directly.
- -F ssh_config specifies an alternative ssh configuration file, this parameter is passed directly to ssh.
- -i identity_file Read the key file used during transmission from the specified file. This parameter is passed directly to ssh.
- -l limit Limit the bandwidth that the user can use, in Kbit/s.
- -P port specifies the port number used for data transmission
- -S program Specifies the program used for encrypted transmission. The program must be able to understand the options of ssh(1).
Four, use examples
Environmental information:
| Remote server IP | 47.100.247.240 |
|---|---|
| Remote server login user | testuser |
| The path of the remote server file | /home/testuser/ |
| Remote server file name | test.sql |
| Local server file path | /home/testuser1 |
| Local server file name | test1.sql |
- Copy remote server files to the current path of
the local server . In the current path of the local server, enter the following command, press Enter and enter the login password of the remote server to copy the remote files to the current path of the local server.
$ scp testuser@47.100.247.240:/home/testuser/test.sql .
- Push local server files to remote server
In the current path of the local server, enter the following command, press Enter and enter the login password of the remote server to copy the local files to the specified path of the remote server.
$ scp test1.sql testuser@47.100.247.240:/home/testuser/
- Copy all the remote server folders to the local server
$ scp -r testuser@47.100.247.240:/home/testuser/ .
- Copy all the local server folders to the remote server
$ scp -r /home/testuser1/ testuser@47.100.247.240:/home/testuser/
Article reference:
Detailed explanation of scp command